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The BA-3 as preamp build guide
The BA-3 as preamp build guide
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Old 9th November 2018, 12:45 AM   #1211
anhton82 is offline anhton82  Viet Nam
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Quote:
Originally Posted by JeffYoung View Post
In a push-pull design the voltage the coupling cap is blocking is only the DC offset (ie: the difference between ground and the centre point of your push-pull). In an ideal world that would be 0 (and there would be nothing to block), but in practice differences between components (and in particular between complementary P and N pairs) means it can be a few volts.

The other thing to consider is what happens if one of your output MOSFETs fails. Depending on the failure mode the DC offset could rise to your + or - rail voltage.

So, even though the cap will normally only be blocking a few volts, it's best to spec it at your rail voltage. Since that's still well under 150V, the mentioned cap would be fine.

Cheers,
Jeff.
Many thanks for your detail explain. I'm a newbie. And this is my first DIY preamp, before that, I finished my first +_15V PSU ( Salas UltraBiB V1.3 ) for Allo Katana DAC. I'm glad to joining you guys DIY world.
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Old 9th November 2018, 07:34 AM   #1212
anhton82 is offline anhton82  Viet Nam
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And one more question, Can I use 100k Volume for this preamp?
Thanks !
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Old 9th November 2018, 02:18 PM   #1213
Russellc is offline Russellc  United States
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The BA-3 as preamp build guide
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Originally Posted by McQuaide View Post
Thanks, added to my Mouser project along with Silmics and MKPs to try.
I like one of Zenmod's favs, the Philips MKC very reasonable and sound very nice. Just ordered a bunch off Ebay in 1.0 and .1 uf for bypass duty.

Russellc
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Old 9th November 2018, 04:33 PM   #1214
McQuaide is offline McQuaide  United States
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Originally Posted by WKCox View Post
+1 on the CDE polypropylene. I used these in a recent recap of my Audio Research / Dynaco ST-70-C3 with excellent results.

I'd like to put these for my Fisher tube amp in .047uF but all they have is 2KV - is there any disadvantage to using a 2KV cap to replace a 400v?
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Old 9th November 2018, 04:36 PM   #1215
ggetzoff is offline ggetzoff  United States
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The BA-3 as preamp build guide
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Originally Posted by McQuaide View Post
I'd like to put these for my Fisher tube amp in .047uF but all they have is 2KV - is there any disadvantage to using a 2KV cap to replace a 400v?

Higher cap service voltage is fine. Probably lower ESR.
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